William s



No. 620,309. Patented Feb. 28, I899,

w. s. HADAWAY, JR.

ELECTRIC FUSE.

(Application filed Apr. 27, 1898.)

(No Model.)

UNITED STATES.

PATENT OFFICE.

.WILLIAM S. HADAWAY, JR, OF NEW YORK, N. Y.-

s-Ls'c'i'mc FUSE..

srncrmcanox formi m of Letters Patent No. 620,309, dated February 28,1899.

Application filed Apri127,1898.

. J r.-, a citizen of the United States,.residing at NewYor-k, county ofNewliorli, State of New York, have inventedcertain new and usefulImprovements in Electric Fuse, fully described and represented in thefollowing specification and the accompanying drawings, forming a part ofthe same.

The object f the present improvement is to secure the conversion of thefuse wire or strip into an insulating substance below the temperature atwhich the fuse will melt and tothus avoid the formation and dispersionof heated particles which may do injury to surrounding objects. Thisresult is obtained in the present invention by employing the metalmagnesium to constitute the entire fuse or as a coating for a fuse-stripof other metal, as

copper, the magnesium in the latter case producing a decomposition ofthe copper with great rapidity and at a definite temperature greatlybelow that at which the copper would fuse. I have discovered thatmagnesium will combine rapidly with the oxygen of the atmosphere whenheated by the electric current to a temperature which isbelow themeltingpoint'of the magnesium. The oxidation of the metal progressesat-a more rapid rate when the air is under a pressuregreater than thatof the atmosphere, and such increased pressure is secured in thepresentinvention by confining the fuse-wire in a tight chamber in which thepressure of the contained air isincreased by the heat generated in thefuse.v

'The' temperature at which the magnesium is oxidized may be governedwith still greater accuracy by coating the magnesium of the fuse with alayer or shell of oxygen-bearing material, such as binoxid of manganese,(MnO which gives up its oxygen at a deli nite temperaturebelow themelting-point of magnesium. When a fusewire or strip conducting acurrent with high voltage is melted by an excess of current, an arc issometimes formed between the several particles of the melted metal andis thus extended by ste s over the space between the circuit-termina s.The operation of my fuse is entirely different, as'its whole exterior isfirst converted into magnesia'by the oxidizing action, thus dimin-Serial so. 878,998. on as.)

ishing the cross-section of the fuse wire or strip and the amount ofcurrent carried thereby. wire carries less and less current until theconversion is complete and the current is wholly. interrupted! The highconducting power of copper makes it'most desirable for As the oxidationprogresses the entire.

a fuse; but experience hasv shown thata cop-- per fuse is graduallydeteriorated by the oxygen of-theatmosphereywhich is combined with thecopper at a temperature considerably below that due to its carryingcapacity.

The capacity of the. fuse is thus gradually d i. 'minished, so that itis liable to be burned out by a current which it was designed to carrywith safety. By coating the copper wire with magnesium its oxidation anddeterioration are wholly prevented and it is adapted for use as a fuseat a'temperature far below the meltingpoint of copper by the burningaway of the magnesium at such low temperature, which I operates toreduce the carrying capacity of the fuse, while the temperature of thebnrnin g magnesium also raises the temperature (it the copper andproduces a rapid oxidation'and conversion of the latter into anon-conductin g substance. The magnesium coatinguponthe copper serves toremove man'yiofthe objections to this type of fuse' in that thetemperature produced by the electric. current cannever exceed that ofthe melting-point of mag nesium, and the combination of the magnesiumwith the copper furnishes an effective means- 0f varying the time factorwith an overload of current, as the time required to burn out the fuseis decreased in proportion as the thickness of the magnesium coating isincreased. The fuse is thus converted into a mass of insulating materialwhich forcibly re sists the passage of current and afiojrds noterminals, and my construction is thus peculpoints to conduct an are bysteps between the iarly adapted for use with high-voltage cur I rents.To prevent positively the formation of an are between the terminals withcurrents of high voltage, the chamber in which the fuse (with a limitedbody of air) is inclqsed may be.

intercepted by'one or more diaphragms of 'in- I sulating material, ascompressed fused magnesia or carbid of silicon. The fuse passes {throughsuch diaphragms, and when it is con- IOO verted into magnesia theproduct fills the perforations in the diaphragms and operates toobstruct the passage of an arc, and thus prevents the formation ormaintenance of an are between the terminals.

These improvements will be understood by reference to the annexeddrawings, in which- Figure 1 is an elevation, and Fig. 2 a longitudinalsection, of a fuse with inclosing tube. Fig. 3 is a longitudinal sectionof a similar construction with diaphragms inserted in the tube. Fig. 4:is a longitudinal section of an ordinary f use-block with the magnesiumwire joined to the circuit-terminals upon screwstuds. Fig. 5 is alongitudinal section of a copper fuse-strip coated with magnesium,

and Fig. 6 is a longitudinal section of such a strip coated withmanganese binoxid.

A designates a tube of vulcanized fiber or other insulating substance,and B porcelain plugs cemented in the ends of the tube and.

having the fuse-terminals 0 extended through the same. I find thatsilicate of soda mixed with fine sand forms a pasty cement adaptedtogecure the plugs firmly in the ends of the tn e. t

D designates the fuse wire or strip, formed of the metal magnesium andattached to the terminals in any suitable manner. The outer ends of theterminals 0 are formed in any suitable manner to make connection withthe circuit-wires, the form shown in the drawings being adapted to clampin spring-holders in the usual manner. I

The plugsB confine the air within the tube, so that when heated by arise oftemperature in the fuse the pressure of the air is increased andthe oxidation of the metal when com menced at a suitable temperature ismore rapid than with air at a normal pressure.

In Fig. 3 four diaphragms are shown inserted within the tube between theplugs B, the diaphragms being readily molded of suitable form with acentral perforation to permit the passage of the fuse wire or strip. Thewire is fitted snugly to the perforation, so that when itis con vertedinto magnesia, which results in considerable expansion of its volume,the passage through the diaphragm is closed by the insulating substancethus formed. As the fuse is heated uniformly throughout its entirelength when traversed by an excess of current, it is convertedsimultaneously into magnesia throughout its entire length, and aftersuch conversion there -is nothing remaining within the fuse-tubc toconduct the current or to initiate the formation of an are.

If the fuse wire or strip were broken at an y point during theconversion and an arc were formed at such point, the are would beultimately broken by the further conversion of the stri p into magnesiaand the plugging of the holes in the diaphragms, which would each assistin resisting the passage of the arc.

l have found that the diaphragms perform an additional function inmodifying or affecting the time required to discharge or break the fuse,as the wire heats more rapidly when unconfined between its terminals andexposed wholly to the air than when intersected by the diaphragms, whichcause it to heat more slowly. Where the fuse without the diaphragmswould be broken in one minute with a given current, the interposition ofa suitable number of the diaphragms will operate to extend the time toone and a half minutes or two minutes, whichever may be desired. Thediaphragms thus adapt the fuse for use with currents of high voltage andserve to regulate the time within which an excess of current may bemaintained in the circuit.

Fig. 4 shows the ordinary bug cut-out,havin g a porcelain body F andcover G,with studs H, upon which the terminals C are wound, as well asthe ends of the fuse-wire D. In this construction the magnesium wire orstrip when converted into magnesia becomes a nonconductor of electricityand heat and furnishes no products of a dangerous character adapted toinjure surrounding objects if it be displaced from its supports.

Fig. 5 shows the composite fuse formed of a wire or strip D of copper orother metal with a coating of magnesium D. Such strip may be used in anyof the constructions shown, operating as follows: The magnesium burnsoff when the temperature reaches the intended point, and the combustionof the magnesium raises the temperature of the other metal, which isalso being rapidlyraised by the electric current, owing to the burningaway of the magnesium. The joint effect of such combustion and of thecurrent upon the copper core is to speedily break the latter and openthe circuit.

Fig. 6 shows the composite strip coated with binoxid of manganese Dwhich is preferably applied in a pastyform with any suitable adhesivemedium and dried upon the fuse strip, so as to adhere permanently.

All the oxids of manganese give up a part of their oxygen at atemperature which is considerably below the melting-point of magnesium,and the binoxid of manganese when decomposed by heat forms protoxid ofmanganese and sets free at a definite temperature a proportion of oxygenwhich unites rapidly with the magnesium and converts it into magnesia.This in the case of the composite wire reduces the carrying capacity ofthe fuse-strip and increases the temperature of the copper or othermetallic core, so as to burn it out rapidly.

The association of the magnesium with the binoxid of manganese producesa fuse whose burning-point can be regulated in the most definite manner,as the decomposition of the oxid occurs at a known point. As the bioxidof manganese operates by combination with the magnesium, it may ofcourse be applied to a solid magnesium fuse-strip like that shown inFig. 2. A time having a magnesium body or covering may be combined -inFig. 6, as it consumes less of the binoxid and avoids the use of aconfining-tube.

-The composite fuse formed of copper or other metal'with magnesiumcoating and having a coating of manganese binoxid may be advantageouslyused within the air-tight tube A, as'shown in Fig. 2, as the copperaflords a conductor of the smallest dimensions'for a given capacity,while the magnesium pre vents the deterioration of the copper andsecures the burning of the fuse at a temperature below itsmelting-pointand without the formation of an arc, while the binoxid of manganeseregulates in the closest manner the temperature at which thecircuitshall be broken.

From the above description it will be seen that the magnesium wire orstrip employed a in my construction is not fused or melted at all,although I have termed it a.fuse wire or strip herein, because the termfuse is generally employed for thermal devices for interrupting anelectric circuit when an excess of current is formed in the same.

The primary feature of my invention is the use in an electric fuse ofmagnesium which oxidizes below the point of fusion, and the secondaryfeatures of the invention are the use of such magnesium as a coating forcopper or'othcr metal and the combination with the magnesium of acoating of manganese binoxid to eilcct the oxidation of the magne siumat a perfectly definite temperature dependent upon the heatingof'thebinoxid.

Having thus set forth the nature of the invention, what I claim hereinis 1. Inan electric "fuse, a inagnesiumwire or strip employed to couductand to break the current, and adapted to oxidize below the point offusion, and. thus forming an infusible conductor under such conditions,substantially as set forth.

2. An electric fuse comprising an insulating-tube with plugs at the endshaving fuseterminals projected through the same, a series of magnesiadiaphragms fitted within the tube between the plugs and a magnesium wire.or strip extended through the diaphragms,

substantially as herein set forth.

3. An electric fuse of copper or other metal having a coating ofmagnesium adapted to oxidize below the f using-point of magnesium, andthus to heat the metallic core while diminishing the capacity of thefuse-strip, substantially as herein setforth.

4. An electric fuse having a magnesium body or covering, in combinationwith an environment of manganese binoxid adapted to furnish oxygen tooxidize the magnesium at a definite temperature, substantially as hereinset forth.

In testimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

WILLIAM S. HADAWAY, JR.

Witnesses:

EDWARD F. Kmsnv, THOMASS. CRANE.

